Autism Spectrum Disorders (ASDs) are lifelong neurodevelopmental conditions with mostly unknown etiology that have a huge impact on affected individuals and their families, and are a major public health concern. This proposal, Autism Spectrum Disorder: Birth Cohort 1976-2000, Epidemiology and Adult Status, in response to NIH Funding Opportunity Announcement (PA-10-158) describes an epidemiologic, population-based, large birth cohort study of ASDs. Significant gaps exist in the knowledge of ASD incidence and its possible rising trend. Detailed characterization (phenotype) of ASD incident cases and ASD subtypes [Autistic Disorder (AD), Asperger's Syndrome (AS) and Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS] is sparse, and potential risk factors (etiologies) are still unknown. Knowledge about adult outcomes of incident ASD cases identified in childhood is almost non-existent. ASD-associated medical costs are high, yet information to improve cost-effective medical management is lacking. A unique set of circumstances, including an already established population-based birth cohort of all children born 1976-2000 to mothers residing in Olmsted County, MN (N=43,934), access to complete, detailed school records for each child in the birth cohort (Independent School District ISD #535 - 41 public, private, home schooled), access to detailed medical records for every child in the birth cohort (Rochester Epidemiology Project-REP; NIH-AR30582), and the Olmsted County Healthcare Expenditure and Utilization Database (OCHEUD) provide the infrastructure to enable the successful completion of this project. This rigorous epidemiologic study involves an experienced multi-disciplinary research team, confirmation of the availability of documented behavioral symptoms of ASD from 1976 forward, with development of a detailed dictionary of descriptive phrases abstracted from medical/school records congruent with DSM-IV-TR criteria (pilot data) and a unique population-based birth cohort. [To help control for changes in special education laws and DSM criteria] this proposal will implement a systematic page by page review of medical and school records of all potential ASD cases regardless of initial school and medical classification and will apply the same uniform research criteria for ASD incident case identification (including DSM-IV-TR criteria), during the 37year study period. We will study the putative rise in incidence of ASD over 37 years, the possible role of certain risk factors on any incidence trend of ASD over time, the shared risk hypothesis by estimating the interaction between perinatal risk factors and family history (parents, siblings) of psychiatric disorders, assessing adult ASD current status and outcomes and cost effective medical management analyses. The knowledge achieved through this combined retrospective and prospective epidemiologic approach will substantially advance scientific/clinical knowledge about ASD. .